Fiber-optic chemical sensing has been demonstrated with a side-polished single-
mode optical fiber, evanescently coupled to chemically sensitive Langmuir-
Blodgett (LB) overlay waveguides. The sensors exhibit a channel-dropping
response centered on a wavelength that is dependent on the thickness and the
refractive index of the overlay waveguide. It has been shown that pH-sensitive
organic dyes proved to be suitable materials fur the formation of an overlay
waveguide whereas LB deposition provides the required thickness control. A
theoretical model of the sensor response, based on the Kramers-Kronig relations
and phase matching of the guided modes within the optical fiber and overlay
waveguide, shows good agreement with experimental results.